Infrared Absorption Spectra of Liquid Crystals

The integral intensity temperature dependence of many various IR bands in crystal, nematic crystal and isotropic phases was investigated. It was found that in the crystal phase 20–40° below the phase transition crystal-nematic crystal all bands investigated decrease nonlinearly. From these changes the activation energy V 2, for a transition of the molecule from the lattice site into an interstitial one was obtained. In liquid crystal phase the bands, corresponding to the benzene ring deformation, do not change or slightly decrease with temperature while those of O-R and Ph-O stretch vibration decrease very rapidly. An attempt was made to connect the temperature behavior of the integral intensity with intermolecular forces in nematic phase.